The goal of this grant proposal is to use newly developed transgenic mouse models to 1) elucidate the role of keratocan-expressing cell lineage in corneal morphogenesis during development and in the maintenance of corneal stromal homeostasis in adult and 2) to investigate TGF? receptor type II (T?RII)-mediated signaling within keratocan- expressing cell lineage during and following development. To manipulate in vivo the mouse genome in a keratocyte-specific manner, a novel transgenic mouse line, Kera-Cre, has been established to carry out Cre-mediated genetic loss-of-function and/or gain-of-function in keratocan-positive cell lineage at given time in vivo. With this model system, we will use Kera-Cre/STOP-DTRed double- transgenic mice to specifically ablate keratocan-positive cell lineage during and following development to test a hypothesis that keratocytes play a central role in corneal morphogenesis and maintenance of corneal homeostasis. We will also use Kera- Cre/TbRIIfloxed/floxed double-transgenic mice to specifically eliminate T?RII signaling within keratocan-expressing cell lineage to test a hypothesis that TGF? signaling plays critical role within keratocytes during corneal morphogenesis. Additionally, we will utilize doxycyclin-inducible mouse model, Kera-rtTA/tetO-Cre/TbRII floxed/floxed triple- transgenic mice to specifically eliminate TbRII signaling within keratocyte to test a hypothesis that TGF2 signaling plays critical role on corneal stromal homeostasis in adult. The aforementioned novel transgenic mouse models, for the first time, will allow us to considerably streamline research regarding the role of keratocan-positive cell lineages during and following corneal development. These proposed studies will provide important insight into the role of keratocytes in supporting corneal stromal function. Another benefit will be the delineation of the functions mediated by the TGF2 signaling pathway within keratocytes during corneal regeneration following injury and keratocyte loss. Furthermore, insight will be obtained regarding the prevention of corneal scarring following injury, which will aid in the design of novel corneal disease treatment regimens. The development of novel cell lineage-specific gene manipulation in transgenic mice, for the first time, will allow us to considerably streamline research regarding the role of keratocan-positive cell lineages during and following corneal development. These proposed studies will provide important insight into the role of keratocytes and TGF? signaling pathway within keratocytes in supporting corneal stromal function. Furthermore, insight will be obtained regarding the prevention of corneal scarring following injury, which will aid in the design of novel corneal disease treatment regimens.